The effect of target annealing temperature on optical and structural properties and composition of CdS thin films prepared by pulsed laser

We studied the effect of target annealing temperature on optical and structural properties and composition of CdS thin films prepared by pulsed Nd:YAG laser. Deposited samples from annealed targets at 300 °C showed a mixed cubic and hexagonal structure, a band gap of about 2.56 eV and Cd/S ratio equal 1. This ratio increased to 2.40 and its band gap decreased to 2.46 eV when the sample was annealed at 500 °C for 1 h in air. However, films prepared from annealed targets at 500 °C became dark due to existence of polymorphous phase of CdO. Films changed to transparent yellow color with a hexagonal CdS structure and some peaks related to CdO after annealing above 250 °C in air. Its band gap value increased from 2.36 eV to 2.41 eV after annealing at 250 and 500 °C respectively.